/-/Aq^  .3-;b  / 


O.  E.  S.  i.lBRARY-  '^^-  ^ 


CONNECTICUT 


ICUIIURAL  EXPERIMEEI  SIMIOI 


NEV/     HAVEN,    CONN. 


BULLETIN   157,  SEPT.,   1907. 


LEAD  ARSENATE  AND  PARIS  GREEN. 

I.    Their  Chemical  Composition.     By  John  Phillips  Street,  M.S. 

II.     Directions  for  their  XJsq  as  Insecticides. 

By  W.  E.  Britton,  Ph.D. 


CONTENTS.  PAGE 

Lead  Arsenate 4 

Analyses  of  Lead  Arsenate 5 

Home-made  Lead  Arsenate 7 

Advantages  in  Using  Lead  Arsenate 7 

Paris  Green .    8 

Analyses  of  Paris  Green 9 

Application  of  Lead  Arsenate  and  Paris  Green 12 

Formula  for  Lead  Arsenate -,  12 

Formula  for  Paris  Green 13 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Con- 
necticut who  apply  for  them,  and  to  others  as  far  as  the  editions 
permit. 


CONHECTICDT  AGRICOLTURAL  EIPERIMENT  STATION, 


BOARD   OF   CONTROL. 
His  Excellency,  Rollin   S.  Woodruff,  Ex  officio,  President. 

Prof.  H.  W.  Conn   Middletown. 

Prof.  W.  H.  Brewer,  Secretary  New  Haven. 

B.  W.  Collins   Meriden. 

Charles  M.  Jarvis   Berlin. 

Edwin  Hoyt   New  Canaan. 

J.  H.  Webb  Hamden. 

E.  H.  Jenkins,  Director  and  Treasurer New  Plaven. 


STATION    STAFF. 

Chemists. 

Analytical  Laboratory. 

John  P.  Street,  M.S.,  Chemist  in  Charge. 

E.  Monroe  Bailey,  M.S.  Kate  G.  Barber,  Ph.D.,  Microscopist. 

Laboratory  for  the  Study  of  Proteids. 
T.  B.  Osborne,  Ph.D.,  Chemist  in  Charge.        C.  A.  Brautlecht,  Ph.B. 

Botanist. 
G.  P.  Clinton,  S.D. 

Entomologist. 
W.  E.  Britton,  Ph.D. 

Assistant  in  Entomology. 
B.  H.  Walden,  B.Agr. 

Forester. 
Austin  F.  Hawes,  M.F. 

Agronomist. 
Edward  M.  East.  Ph.D. 

Stenographers  and  Clerks. 

Miss  V.  E.  Cole. 
Miss  L.  M.  Brautlecht. 
Miss  E.  B.  Whittlesey. 

In  charge  of  Buildings  and  Grounds. 
William  Veitch. 

Laboratory  Helper. 
Hugo  Lange. 

Sampling  Agent. 
V.  L.  Churchill,  New  Haven. 


LEAD  ARSENATE  AND  PARIS  GREEN. 


I.     THEIR  CHEMICAL  COMPOSITION. 

By  Joiln  Phillips  Street.* 

The  constantly  increasing  use  of  insecticides  in  various  spray- 
ing mixtures  makes  the  effectiveness  and  the  cheapness  of  the 
poisons  used  a  matter  of  considerable  practical  importance.  Paris 
green  has  been  more  commonly  used  for  many  years  than  any 
other  arsenical  insecticide,  and  has  proved  very  effective.  There 
is,  however,  a  certain  serious  objection  to  its  use;  the  partial 
solubility  in  water  of  the  arsenious  oxid,  which  frequently  causes 
damage  to  foliage.  Fot  this  reason  entomologists  have  sought  a 
different  poison,  which  would  be  effective  against  insects,  harm- 
less to  plants,  and  economiical  for  the  farmer  to  use.  Lead 
arsenate  seems  to  meet  these  requirements,  and  possesses  a  still 
further  advantage  over  Paris  green  in  that  its  mechanical  condi- 
tion keeps  it  longer  in  suspension  in  the  spraying  mixture. 
There  are  a  number  of  brands  of  this  material  on  the  market, 
varying  greatly  in  appearance  and  consistency,  and  it  was  con- 
sidered advisable  to  make  a  somewhat  extended  chemical 
examination  of  them  to  determine  their  relative  value.  As  the 
various  brands  of  Paris  green  on  sale  in  this  State  had  never  been 
analysed  at  this  Station,  they  also  have  been  included  in  this 
examination. 

METHODS   OF  ANALYSIS. 

In  the  analysis  of  lead  arsenate  the  method  proposed  by  Hay- 
woodf  has  been  followed  in  all  particulars,  and  has  proved  very 
satisfactory.  With  Paris  green  the  same  methods  as  used  by  the 
writer^  in  a  similar  examination  at  the  New  Jersey  Station  have 

*  The  anal3'^ses  of  Paris  green  have  been  made  by  Messrs.  E.  M.  Bailey 
and  E.  T-  Shanley  ;  those  of  lead  arsenate  by  the  writer. 
t  U.  S.  Dept.  of  Agl.,  Bur.  of  Chem.,  Bull.  105,  165. 
X  New  Jersey  Expt.  Station,  Bull.  195. 


4  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    1 57. 

been  followed.  In  addition,  however,  a  test  of  the  water-solu- 
bility of  the  arsenious  oxid  was  made  by  the  official  A.  O.  A.  C. 
method,*  treating  the  green  with  distilled  water  for  ten  days. 

LEAD   ARSENATE. 

Ten  of  the  eleven  samples  analysed  were  taken  from  the 
museum  stock  of  Dr.  Britton,  the  State  entomologist,  but  were 
recently  acquired  and  were  believed  to  be  representative ;  the 
duplicate  sample  of  Swift's  arsenate  w^as  bought  in  the  open 
market.  The  samples  were  received  in  containers  of  various  sizes 
and  material,  from  a  one-pound  glass  jar  to  a  fourteen  pound 
wooden  bucket.  The  material  itself  showed  striking  differences 
in  consistency.  Disparene  settled  out  completely,  leaving  a 
supernatant  liquid  filling  from  one-fourth  to  one-third  of  the 
vessel ;  the  Target  brand  and  Swift's  also  showed  some  separated 
liquid,  while  the  others  were  more  of  the  consistency  of  putty 
and  quite  homogeneous. 

The  samples  analysed  were  as  follows : 

19210.  Eagle  Brand.  Adler  Color  &  Chemical  Co.,  Xew 
York. 

19212.  Target  Brand.  American  Horticultural  Distributing 
Co.,  Martinsburg,  W.  Va. 

19211.  Disparene.     The  Bowker  Co.,  Boston,  Mass. 
19216.     Star  Brand.     Fred.  L.  Lavanburg,  New  York. 
19215.     Anchor  Brand.     Leggett  &  Bro..  New  York. 

19213.  Swift's  Arsenate.  ]\Ierrimac  Chemical  Co.,  Boston, 
Mass. 

18703.     Duplicate  of  No.  19213,  purchased  in  market. 
19643.     Arsenate    of     Lead.      Monmouth    Chemical     Works. 
Shrewsbury,  N.  J. 

19357.  Arsenate  of  Lead.  The  Powers-\\'eightman-Rosen- 
garten  Co.,  Philadelphia,  Pa. 

19358.  Aiboneta.  Schoonmaker  &  Son,  Cedar  Hill-on-Hud- 
son,  N.  Y. 

19209.  Arsenate  of  Lead.  The  Vrceland  Chemical  Co..  New 
York. 

*  U.  S.  Dept.  of  Agl.,  Hur.  of  Cliem..  Circ.  lo,  3. 


ANALYSES    OF    LEAD    ARSENATE. 
Analyses  of  Arsenate  of  Lead. 


19210 
19212 
19211 
19216 
19215 
19213 
J  8703 
19643 
19357 
19358 
19209 


Eagle 

Target 

Disparene 

Star 

Anchor. 

Swift's 

Monmouth 

Powers-Weightman 

Aiboneta 

Vreeland    -..-.    .- 


Original  Material. 


54-55 
50.30 
46.47 
50.57 
35-59 
49-95 
48.40 

58.44 
51-79 
41-95 
33-65 


14.89 
12.30 

13.87 
12.64 
17.11 
14-91 
15-19 
11.29 
11. 42 
ri.72 
21. gi 


0.32 
2.73 

4-34 
0.47 
2.02 
o.So 
0.88 
1. 41 
2.69 

7-94 
0.74 


1.78 
0.64 
0.21 
0.69 
1.23 
1.26 
1.75 
3-27 
0.40 

0.49 
2.26 


— -o 


0.46 

I-3I 

0-39 
0.51 
0.86 

0-57 
0.30 
0.50 
0.22 
0.42 
0.86 


32.76 
24-75 
25.91 
25.57 
26.56 
29.79 
29.44 
27.17 
23.69 
20.19 
33.02 


62.62 
68.47 
65-59 
72.08 

68.  ",9 
66.09 

65-47 
61-57 
69  90 
65.29 
62.46 


4.62 
6.78 
8.50 
2-35 
5-05 
4.12 

5-09 
11.26 

6.41 
14-52 

4.52 


RESULTS  OF  ANALYSES. 

The  analyses  show  lead  arsenate  to  be  far  from  a  uniform 
material;  the  arsenic  oxide  ranges  from  11.29  to  21.91  per  cent., 
and  the  lead  oxide  from  25.59  to  44.05  per  cent.  The  soluble 
arsenic  oxide  was  low  in  all  cases,  ranging  from  0.22  to  1.31  per 
cent.,  and  this  after  a  treatment  for  ten  days.  No  soluble  lead 
oxide  was  found  in  any  of  the  samples.  The  nature  of  the  impuri- 
ties was  not  determined  in  any  case ;  19210,  19358,  19643  and 
19357,  however,  showed  traces  of  nitrates.  The  impurities  were 
not  high  except  in  three  samples,  19211,  19643  and  19358;  neither 
Disparene  nor  Aiboneta  was  sold  as  pure  lead  arsenate  and  there- 
fore cannot  be  considered  adulterated ;  the  Monmouth  sample, 
however,  was  sold  as  a  pure  material ;  in  addition  to  its  high 
content  of  impurities,  it  also  contains  the  lowest  percentages  of 
both  arsenic  and  lead  oxids. 

Lead  arsenate  is  usually  prepared  by  the  action  of  lead  acetate 
on  disodium  arsenate ;  some  manufacturers,  however,  substitute 
lead  nitrate  for  the  acetate.  Smith*  has  shown  that  the  com- 
mercial grades  of  sodium  arsenate  and  lead  acetate  and  nitrate 
vary  considerably.  He  found  the  lead  oxide  in  lead  acetate  varied 
from  58.81  to  66.80  per  cent.,  and  in  lead  nitrate  from  66.37  ^ 
*  Agr.  Massachusetts,  1897,  357-369. 


6  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    1 57. 

68.37  l^'-"''  cent. ;  while  in  sodium  arsenate  the  arsenic  oxid  varied 
from  36.77  to  47.80  per  cent.  The  calculation  of  the  theoretical 
composition  of  commercial  lead  arsenate  is,  therefore,  attended 
with  some  difficulty.  Haywood,"^'  however,  has  shown  that,  with 
pure  chemicals,  where  lead  acetate  is  used  the  theoretical  com- 
position should  be  74.40  per  cent,  lead  oxide  and  25.60  per  cent, 
arsenic  oxide;  and  wdiere  lead  nitrate  is  used.  64.26  and  33.15 
per  cent.,  respectively.  The  methods  used  in  the  above  analyses 
give  results  very  close  to  theory  wdiere  the  lead  arsenate  is  pre- 
pared from  lead  nitrate,  but  where  lead  acetate  is  used  slightly 
higher  than  theory  for  arsenic  oxide  and  slightly  lower  for  lead 
oxide,  indicating  that  probably  some  secondary  reaction  takes 
place  during  the  process  of  manufacture,  resulting  in  the  forma- 
tion of  some  compound  other  than  lead  arsenate,  probably  an 
acid  lead  arsenate.  By  referring  to  the  analyses  of  the  samples 
on  the  water-free  basis,  it  appears  that  18703,  19209.  19210, 
19213  and  19643  are  made  from  lead  nitrate,  the  others  from 
lead  acetate.  Formerly  it  was  the  practice  to  add  glucose  to 
increase  the  adhesive  power  of  the  arsenate,  but  it  has  been 
sliown  that  it  adheres  almost  as  well  without  glucose  as  with  it. 
and  its  use  has  been  largely  discontinued. 

Allowing  for  the  variations  in  process  of  manufacture,  it 
would  seem.  hoA^ever,  that  the  content  of  arsenic  oxid  in  the 
various  commercial  lead  arsenates  was  conditioned  more  by  the 
wetness  of  the  material  than  anything  else ;  the  content  of  water 
in  the  samples  analysed  ranged  from  33.65  to  58.44  per  cent. 
A  perfectly  dry  material  has  not  been  found  advantageous,  for 
while  even  in  such  a  form  it  remains  in  suspension  several  times 
as  long  as  the  finest  Paris  green,  it  settles  about  three  times  as 
fast  as  when  the  arsenate  is  used  in  the  form  of  a  paste.  On 
the  other  hand,  the  paste  must  not  be  too  tenacious  ov  it  will  be 
difficult  to  lireak  up  and  distribute  evenly  throughout  the  spray- 
ing mixture.  Colby f  has  found  this  objection  to  hold  with 
Disparene.  In  making  the  water-soluble  determinations  it  was 
observed  that  there  were  marked  variations  in  the  rate  of  settling 
even  when  the  samples  were  ui  the  dry  and  powdered  condition. 
It  is  probable  that  the  same  peculiarity  would  have  ])een  noted 
in  the  samples  in   Iheir  original  stale.  Init  as  in  most  cases  the 

*  U.  S.  Dept.  of  AgL,  Bur.  of  Clicm..  Bull.  105.  ibS. 
f  California  Expt.  Station,  Bull.  151. 


ANALYSES    OF    LEAD-   ARSENATE.  7 

whole  sample  had  already  been  dried,  verification  of  this  sup- 
position was  impossible. 

HOME-MADE  LEAD  ARSENATE. 

It  has  frequently  been  recommended  that  farmers  prepare 
their  own  lead  arsenate  as  they  need  it.  Colby*  recommends 
the  following  formula :  Dissolve  24  oz.  of  lead  acetate  or  20  oz. 
of  lead  nitrate  in  one  gallon  of  cold  water;  also  separately  dis- 
solve 10  oz.  sodium  arsenate  in  three  quarts  of  water,  both 
solutions  to  be  made  in  wooden  vessels.  Pour  the  separate 
solutions  into  the  spray  tank  containing  from  100  to  150  gallons 
of  water ;  a  white  precipitate  of  lead  arsenate  im^mediately  forms. 
This  preparation  may  be  made  several  times  stronger  without  the 
least  danger  of  injury  to  the  foliage.  The  freshly  precipitated 
home-made  arsenate  seems  to  keep  in  suspension  better  than 
even  the  best  commercial  preparations. 

COST  OF  LEAD  ARSENATE. 

As  stated  before,  only  one  oif  the  samples  was  bought  in  the 
open  market ;  the  prices  have  therefore  not  been  affixed  in  any 
case.  By  correspondence  with  the  manufacturers  the  Station 
received  quotations  as  follows:  In  100  lb.  kegs,  from  9.5  to  13 
cents  per  lb.;  in  5  to  20  lb.  buckets,  from  11  to  16  cents  per 
lb.;  and  in  i  lb.  cans  from  11.5  to  17  cents  per  lb.  The 
advantage  of  purchasing  in  quantity  is  apparent. 

ITS  ADVANTAGES. 

Lead  arsenate  is  very  effective  against  leaf-eating  insects.  Its 
chief  advantages  over  Paris  green  are  its  greater  adhesive  power 
and  its  harmlessness  to  the  foliage.  A  single  treatment  of  lead 
arsenate  will  adhere  to  the  foliage  for  a  period  during  which  two 
or  three  sprayings  with  Paris  green  would  be  necessary  to  secure 
the  same  effect.  The  insolubility  of  its  arsenic  makes  possible 
the  use  of  large  quantities  without  danger  even  in  inexperienced 
hands.  From  the  standpoint  of  effectiveness  lead  arsenate, 
although  containing  but  from  one-third  to  one- fourth  as  much 
actual  arsenic  as  Paris  green,  is  nearly  as  economical  as  the  latter 
poison  when  sold  at  the  same  price.  Purchased  at  the  wholesale 
quotations  noted  elsewhere,  and  considering  the  duration  and 
safety  of  its  action,  it  is  actually  somewhat  cheaper  than  Paris 
*  Loc.  cit. 


8  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    1 57. 

green.  Furthermore,  its  greater  power  of  suspension  makes  jt 
more  easily  used  and  insures  a  more  uniform  distribution  of  the 
poison  over  the  plant. 

PARIS  GREEN. 

There  is  no  law  in  this  State  regulating  the  sale  of  Paris  green, 
but  where  a  state  inspection  is  in  effect  the  requirements  are 
generally  very  similar  to  those  in  the  New  Jersey  law,*  section 
3  of  which  reads : 

"  Paris  green,  or  an}'  product  analogous  to  it,  when  sold,  ofTfred  or 
exposed  for  sale  as  such,  in  this  State,  shall  comply  with  the  following 
requirements  : 

"  First.  It  shall  contain  arsenic,  in  combination  with  copper,  equivalent 
to  not  less  than  fifty  per  centum  arsenious  oxide. 

"  Second.  It  shall  not  contain  arsenic  in  water-soluble  forms  equivalent 
to  more  than  three  and  one-half  per  centum  of  arsenious  oxide." 

Many  analyses  of  Paris  green  have  been  made  by  the  various 
Experiment  Stations,  showing  the  green  to  be  of  variable  com- 
position. These  variations  are  chiefly  due  to  different  methods 
of  manufacture  or  carelessness  in  carrying  out  the  same.  In 
many  cases  a  large  amount  of  the  arsenic  exists  as  free  arsenious 
oxid,  which  may  arise  from  intentional  addition  of  white  arsenic, 
as  well  as  from  careless  manufacture.  This  is  a  serious  adul- 
teration, for  white  arsenic  is  a  cheaper  material,  and  its  solu- 
bility in  water  renders  its  presence  in  anything  but  small  quantities 
a  source  of  much  dangler  to  foliage  from  scorching.  Other 
adulterations  have  been  detected,  but  the  one  just  referred  to  is 
the  most  prevalent  and  most  objectionable. 

Paris  green  is  essentially  copper  aceto-arsenite,  and.  if  pure, 
should  contain  an  equivalent  of  58.65  per  cent,  arsenious  oxide, 
31.29  copper  oxide  and  10.06  acetic  acid.  The  commercial  article, 
however,  usuall}''  contains  small  quantities  of  moisture  and  sand 
and  varying  amounts  of  sodium  sulphate. 

Twelve  samples,  representing  eight  manufacturers,  were  pur- 
chased from  dealers  by  the  Station  sampling  agent.  A  descrip- 
tion of  these  follows: 

19481.  Made  by  A.  B.  Ansbacher  &  Co..  Xew  York.  Sold 
by  Lyon  &  Ewald,  New  London. 

'  18662.  Made  by  A.  B.  Ansbacher  &  Co..  New  York.  Sold 
by  the  Sisson  Drug  Co.,  Hartford. 

*  New  Jersey  Expt.  Station,  Bull.  195. 


ANALYSES   OF   PARIS   GREEN.  9 

18634.     Made  by  E.  J.  Barry,  New  York.     Sold  by  Odell's 
Pharmacy,  New  Britain. 

18509.  Made  by  E.  J.  Barry,  New  York.     Sold  by  J.  H.  & 
W.  E.  Cone,  Hartford. 

18704.,    Made  by  James  A.  Blanchard,  New  York.     Sold  by 
F.  S.  Piatt,  New  Haven. 

19547.     Made  by  Morris  Hermann  &  Co.,  New  York.     Sold 
by  D.  B.  Wilson  Co.,  Waterbury. 

18569.     Made  by  Leggett  &  Bro.,  New  York.     Sold  by  Lock- 
wood  &  Palmer,  Stamford. 

18508.     Made  by  Leggett  &  Bro.,  New  York.     Sold  by  ^L  H. 
Mallett,  New  Milford. 

.  18512.     Made  by  L  Pfeiffer,  New  York.     Sold  by  Frank  M. 
West,  Bridgeport. 

18510.  A/[ade  by  C.  T.  Raynolds  &  Co.,  New  York.     Sold  by 
H.  K.  Brainard,  Thompsonville. 

18511.  Made  by  C.  T.  Raynolds  &  Co.,  New  York.     Sold  by 
Danbury  Hardware  Co.,  Danbtiry. 

18663.     Made  by  The  Sherwin-Williams  Co.,  Newark,  N.  J. 
Sold  by  R.  E.  Page,  Hartford. 

Analyses  of  Paris  Grken. 


1 948 1 
18662 

18634 
18509 
18704 

19547 
1S569 
18508 
18512 
18510 
18511 
18663 


Manufacturer. 


Ansbacher. 
Barry 


Blanchard 
Hermann.. 
Leggett  - . . 


Pfeiffer    .. 
Raj'nolds 


Sherwin-Williams 


cts. 

13 
10 

35 
18 
10 
18 
10 
20 
20 
28 

TO 
10 


Weight  of 
Package. 


OZ. 

*4 

4 

*I6 

*  8 

4 

*  8 

*4 
8 
8 

*i6 

*  4 
4 


OZ. 

3.6 
4.0 

14.5 
8.0 


Arsenious  Oxide 

(A.S2O3). 


57-92 

57-44 
57-23 
56.62 


5-0  57  03 
7.6I56.20 


3-6 
7-3 
8,0 

15-4 
4.0 
3.6 


60.61 
56.83 
56.71 
60.83 
61.19 
56.56 


1.46 
0.97 
1. 71 

2-44 
2.44 
2.44 
5-85 
2.92 
1.46 

1-95 
2.44 
1.46 


So 

a  3 
CO 


28.76 
29.49 

29-55 
29.01 
2S.14 
28.54 
27-15 
29-34 
30.27 
26.56 

27-15 

29. 88 


53-78 
55-15 
55-26 

54-25 
52.62 

53-37 
50.77 
54.B7 
56.60 
49-63 
50.77 
55-88 


*  Weight  printed  on  label  ;  in  all  other  cases  the  weight  is  assumed  from 
the  size  of  package  and  price  asked. 


lO  CONNECTICUT    EXPERIMENT    STATION    liULLETIN    1 57. 

All  the  samples  were  carefully  weighed  with  and  without 
the  container;  one  sample  was  overweig-ht,  four  equalled  the 
w^eight  claimed,  and  seven  were  short  weight.  These  shortages 
varied  from  4  to  10  per  cent.,  not  large  in  any  case,  but  indicat- 
ing that  the  manufacturers'  claimed  weight  is  intended  to  include 
the  weight  of  the  container  as  well  as  the  green  itself,  a  practice 
without  justification. 

CHEMICAL  ANALYSIS. 

Total  Arseuious  Oxide.  All  the  samples  contained  satisfactory 
amounts  of  total  arsenious  oxide,  varying  from  56.20  to  61.19 
per  cent,  with  an  average  of  57.93  per  cent. ;  this  average  is 
only  slightly  lower  than  the  equivalent  of  arsenious  ox-ide  con- 
tained in  pure  copper  aceto-arsenite.  Judging,  therefore,  alone 
from  the  content  of  arsenious  oxide,  it  would  appear  that  the 
Paris  green  on  the  market  in  Connecticut  is  of  high  quality.  A 
definite  decision  as  to  the  purity  of  the  green,  however,  cannot 
be  reached  without  considering  also  the  amount  of  water-soluble 
arsenic  present. 

Water-Soliihle  Arsenious  Oxide.  Free  arsenious  oxide  is 
always  soluble  in  water,  and  the  combined  arsenic  is  liable  to  be 
rendered  soluble  by  prolonged  treatment.  Two  methods  for 
determining  soluble  arsenious  oxide  have  been  adopted  pro- 
visionally by  the  Association  of  Official  Agricultural  Chemists, 
in  one  of  which  sodium  acetate  is  used  as  the  solvent,  while  in 
the  other  the  green  is  treated  with  water  for  ten  days.  Investiga- 
tions with  these  methods  have  shown  that  the  sodium  acetate 
method  gives  more  closely  the  true  percentage  of  free  arsenious 
oxide,  while  the  water-extraction  method  gives  in  addition  some 
arsenic  caused  by  the  decomposition  of  the  green  by  water.  From 
a  practical  standpoint  the  portion  of  the  green  that  is  so  loosely 
combined  would  in  all  likelihood  soon  break  up  and  scorch  the 
foliage  quite  as  badly  as  would  free  arsenious  oxide.  The  water- 
extraction  method  would  seem,  therefore,  to  indicate  more 
accurately  the  probable  effect  of  the  green  on  foliage. 

The  provisional  method  of  the  A.  O.  A.  C.  requires  treatmenc 
with  water  for  ten  days,  but  it  has  lieen  pointed  init  that  the  usual 
practice  among  horticulturists  is  to  mix  the  green  with  water 
not  very  long  l^efore  they  wish  to  use  it.  For  this  reason  certain 
Stations,    for   instance  New  York,   California   and   Now    Jersev, 


ANALYSES   OF  PARIS   GREEN.  I  I 

have  adopted  a  one-day  extraction  period,  which  it  is  beheved 
gives  results  more  in  harmony  with  actual  practice.  This  Sta- 
tion has  likewise  adopted  this  method  in  the  present  work,  and 
analyses  by  both  the  one-day  and  ten-day  extractions  are  given 
in  the  table  for  comparison.  The  analyses  clearly  show  that, 
if  the  ten-day  method  is  to  prevail  as  a  standard,  but  three  of 
the  samples  would  fall  within  the  usual  legal  limit  of  three  and 
one-half  to  four  per  cent,  of  soluble  arsenious  oxide.  With  the 
one-day  method,  but  ome  sample,  18569,  contains  an  excessive 
amount,  5.85  per  cent.  This  sample  varies  greatly  in  composi- 
tion from  a  duplicate  sample  from  the  same  manufacturer,  and 
under  the  microscope  clearly  shows  the  presence  of  white  arsenic. 
The  use  of  this  sample  would  be  exceedingly  dangerous  to  foli- 
age. 

Copper  Oxide.  The  amount  of  cupric  oxide  found  in  the 
samples  varied  from  26.56  to  30.27  per  cent.,  with  an  average  of 
28.65  P^^  cent.  In  pure  copper  aceto-arsenite  the  ratio  of 
arsenious  oxide  to  copper  oxide  is  as  1.87  is  to  i.oo.  This  ratio  is 
of  value  in  assisting  to  determine  whether  white  arsenic  has  been 
used  to  fortify  the  green,  for  arsenious  oxide  cannot  be  added 
without  increasing  the  ratio.  In  the  samples  analysed,  the  ratio 
varied  from  1.87  to  2.29;  the  high  ratio  shown  in  sample  18569 
gives  additional  evidence  of  the  presence  of  considerable  quanti- 
ties of  white  arsenic.  The  amiount  of  arsenious  oxide  in  combina- 
tion with  copper  varied  from  49.63  to  55.88  per  cent.,  with  one 
exception  above  the  usual  legal  requirement  of  50  per  cent.  In 
three  of  the  samples  the  amount  of  arsenious  oxide  is  more  than 
2.20  times  that  of  the  copper  oxide,  and  the  natural  inference  is 
that  either  arsenic  has  been  added  purposely  or  that  the  material 
has  been  carelessly  manufactured. 

A  comparison  of  the  water-soluble  arsenic  in  Paris  green  and 
lead  acetate  emphasizes  one  of  the  chief  advantages  gained  by 
using  the  latter  insecticide.  In  lead  arsenate  from  0.22  to  1.3 1 
per  cent,  was  soluble  in  ten  days,  while  in  Paris  green  the  solu- 
bility ranged  from  2.44  to  10.72  per  cent. 


12  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    1 57. 

II.  DIRECTIONS  FOR  THE  USE  OF  LEAD  ARSENATE 
AND  PARIS  GREEN  AS  INSECTICIDES. 

By  W.  E.  Britton,  Entomologist. 

Lead  arsenate  as  an  insecticide  was  first  used  in  the  work  of 
the  Gypsy  ]\Ioth  Commission  in  ^Massachusetts  in  the  early  nine- 
ties and  it  has  since  been  employed  in  controlling  nearly  all  of  the 
leaf-eating-  insects,  and  has  proved  to  be  a  valuable  addition  to 
our  list  of  available  arsenical  poisons.  When  devoured  by 
insects  it  is  somewhat  slower  in  its  action  than  Paris  green,  and 
should  therefore  be  applied  earlier,  before  much  damage  has  been 
done  to  the  plants.  On  account  of  the  excellent  adhesive  qualities 
of  lead  arsenate,  it  remains  upon  the  foliage  for  a  long  time, 
w^hile  Paris  green  soon  washes  off  if  rains  are  frequent.  Lead 
arsenate  is  gradually  replacing  Paris  green  as  an  arsenical  insecti- 
cide, and  especially  during  the  past  season  the  high  price  of  the 
latter  has  induced  many  farmers  and  fruit  growers  to  use  lead 
arsenate.  Paris  green  has  been  used  to  destroy  leaf-eating 
insects  ever  since  the  Colorado  potato  beetle  reached  the  Atlantic 
States.  It  is  therefore  the  old  standard  remedy,  and  in  many 
places  is  the  only  arsenical  insecticide  that  can  be  purchased  at 
the  stores. 

FORMULA  FOR  LEAD  ARSENATE. 

As  lead  arsenate  is  sold  in  paste  form,  and  even  when  cal- 
culated as  w^ater-free  contains  less  arsenic  than  Paris  green,  it  is 
necessary  to  use  a  larger  quantity  by  weight  of  the  commercial 
article  to  gain  the  desired  end  in  spraying  work.  Lead  arsenate 
can  be  used  only  in  liquid  form  to  be  sprayed  upon  the  foliage, 
and  the  usual  formula  is  as  follows : 

Lead  arsenate 3  lbs. 

Water 50  gallons. 

For  sawfl}-  larvae  and  some  other  insects  that  are  easy  to  kill, 
one  pound  in  fifty  gallons  may  suffice,  and  in  spraying  to  kill 
gypsy  caterpillars  five  pounds  in  fifty  gallons  are  the  proportions 
considered  the  most  efi:'ective.     In  spraying  for  elm  leaf  beetle 

larvae  the  poison  should  be  directed  against  the  under  sides  of 


PARIS    GREEN   AS   AN    INSECTICIDE.  1 3 

the  leaves.  The  amount  of  lead  arsenate  may  be  increased  greatly 
without  danger  of  injuring  the  foliage,  and  lime  should  not  be 
added.  Lead  arsenate  can  be  used  in  connection  with  Bordeaux 
mixture,  though  it  is  thought  to  be  slightly  less  effective  as  an 
insecticide  when  used  in  this  way.* 

FORMULA  FOR  PARIS   GREEN. 

Paris  green  is  put  up  in  powder  form  and  can  be  applied  either 
dry  or  as  a  liquid.  On  account  of  the  soluble  acid  which  it  con- 
tains (see  page  9  of  this  bulletin)  there  is  always  danger  of 
"burning"  the  foliage  unless  some  alkali  is  used  with  the  poison. 
For  this  purpose  lime  is  usually  recommended,  and  the  adhesive- 
ness of  the  mixture  is  greatly  improved  by  the  lime.  About  three 
pounds  of  lime  should  be  used  for  each  pound  of  Paris  green. 
If  to  be  applied  dry  in  a  duster  or  powder  gun,  Paris  green  should 
be  mixed  thoroughly  with  air-slaked  lime  or  land  plaster  in  the 
following  proportions : 

Paris  green i  pound. 

Air-slaked  lime _      loo  pounds. 

For  use  as  a  spray  Paris  green  may  be  prepared  as  follows  : 

Paris  green i  pound. 

Fresh  quicklime 3  pounds. 

Water 100  gallons. 

In  most  orchards  and  potato  fields  Paris  green  is  used  in  con- 
nection with  Bordeaux  mixture,  and  as  this  contains  an  excess  of 
lime,  no  more  lime  is  added. 

*  Tests  made  at  this  Station  show  that  the  presence  of  the  Bordeaux 
mixture  renders  the  lead  arsenate  perfectly  insoluble.  This  perhaps  may 
account  for  its  lessened  poisonous  effect  on  insects. 


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